GPSA Ch. 16
| Parameter | Typical Range |
|---|---|
| Flash Pressure | 50–200 psig |
| Flash Temperature | 100–200°F |
| Retention Time | 3–10 min |
| L/D Ratio | 2.5–4.0 |
| KSB (Flash Drum) | 0.10–0.20 |
| Vapor Fraction | 30–80% |
Rachford-Rice Flash Equation:
Solved iteratively for vapor fraction V/F. K-values depend on component volatility and pressure ratio. Methane and ethane preferentially flash; propane and heavier remain in liquid.
Function: The hot rich-oil flash tank liberates dissolved light gases at reduced pressure before the oil enters the purification still. This reduces vapor loading on the still and recovers fuel gas.
Understand hot oil flash systems, absorption oil regeneration, flash drum design, and flash gas recovery
A hot rich-oil flash tank is a vessel where heated rich oil from an absorber is flashed at reduced pressure to release dissolved light gases (Cā, Cā) before entering the oil purification still. It is sized per GPSA Ch. 16.
The calculator uses the Rachford-Rice flash equilibrium method to determine the vapor/liquid split and composition at the specified flash temperature and pressure per GPSA Ch. 16.
Retention time ensures adequate liquid-vapor separation and typically ranges from 3 to 10 minutes depending on oil viscosity and flash severity. The calculator uses retention time with liquid flow rate to size the vessel.
Flash tank vessels are designed per ASME Section VIII for pressure containment. The calculator determines vessel diameter, length, wall thickness, and estimated weight based on design pressure and the Rachford-Rice flash results.